Nitrogen-Containing Low Volatile Compounds from Pinonaldehyde

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Nitrogen-containing low volatile compounds from pinonaldehydedimethylamine reaction in the atmosphere: A laboratory and field study Geoffroy Duporté, Jevgeni Parshintsev, Luis M.F. Barreira, Kari Mikael Hartonen, Markku Kulmala, and Marja-Liisa Riekkola Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b00270 • Publication Date (Web): 01 Apr 2016 Downloaded from http://pubs.acs.org on April 7, 2016

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Environmental Science & Technology

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Nitrogen-containing low volatile compounds from pinonaldehyde-dimethylamine reaction in the

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atmosphere: A laboratory and field study

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Geoffroy Duporté,† Jevgeni Parshintsev,† Luís M. F. Barreira,† Kari Hartonen,† Markku

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Kulmala,‡ and Marja-Liisa Riekkola*,†

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† Laboratory of Analytical Chemistry, Department of Chemistry, University of Helsinki, P.O.

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Box 55, 00014 Helsinki, Finland

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‡ Division of Atmospheric Sciences, Department of Physics, University of Helsinki, P.O. Box

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64, 00014 Helsinki, Finland

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ABSTRACT

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Pinonaldehyde, which is among the most abundant oxidation products of α-pinene, and

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dimethylamine were selected to study the formation of N-containing low volatile compounds

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from aldehyde-amine reactions in the atmosphere. Gas phase reactions took place in a Tedlar

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bag, which was connected to a mass spectrometer ionization source via a short deactivated fused

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silica column. In addition to on-line analysis, abundance of gaseous precursors and reaction

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products were monitored off-line. Condensable products were extracted from the bag’s walls

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with a suitable solvent and analyzed by gas chromatography coupled to chemical ionization

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high-resolution quadrupole time-of-flight mass spectrometry and by ultra-high-performance

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liquid chromatography coupled to electrospray ionization Orbitrap mass spectrometry. The

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reactions carried out resulted in several mid-low vapor pressure nitrogen-containing compounds

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that are potentially important for the formation of secondary organic aerosols in the atmosphere.

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Further, the presence of brown carbon, confirmed by liquid chromatography-UV-Vis-mass

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spectrometry, was observed. Some of the compounds identified in the laboratory study were also

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observed in aerosol samples collected at SMEAR II station (Hyytiälä, Finland) in August 2015

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suggesting the importance of aldehyde-amine reactions for the aerosol formation and growth.

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INTRODUCTION

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Atmospheric aerosols play an important role in regional air quality, have adverse health impacts

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and can affect regional and global climate directly and inderectly.1-3 Primary aerosols are directly

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emitted in the atmosphere from a variety of sources, while secondary aerosols are formed

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through atmospheric oxidation and processing of volatile organic compounds (VOCs) via gas-to-

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particle partitioning.4 Secondary organic aerosols (SOA) have been identified as important

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contributors of atmospheric aerosols.5 Despite continuing studies, the effects of aerosols on

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climate, regional air quality and health are not yet well understood, mainly due to missing

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knowledge of secondary aerosol precursors, chemical composition and mechanisms of SOA

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formation which are today the main challenges in the field of atmospheric aerosols. Among the

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atmospherically relevant compounds, amines have been demonstrated to play an important role

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in new particle formation (nucleation) events and secondary organic aerosol formation.6-8

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Amines are emitted to the atmosphere from industry, combustion, biomass burning, animal

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husbandry and the oceans.6 In addition, soil and vegetation act as their important sources,

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especially during periods with high biological activity.6 These compounds are ubiquitous in the

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atmosphere, as e.g. Ge et al.6 have shown by summarizing 154 identified amines in the

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atmosphere emitted from anthropogenic and biogenic sources. The most abundant amines in the

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atmosphere are low-molecular weight aliphatic amines such as methylamine (MA),

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dimethylamine (DMA) and trimethylamine (TMA). Atmospheric removal pathway for amines


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include oxidation reactions with ozone (O3), hydroxyl (OH) radical or nitrate (NO3) radical9-12

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and reactions with inorganic acids (nitric or sulfuric acids).6-8,

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pressures, they can affect the chemistry and lifecycle of atmospheric aerosols, especially due to

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their unique acid-neutralizing capacity. Many recent studies have highlighted the role of amines

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in the formation of secondary aerosols and growth (nucleation, secondary organic and inorganic

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aerosol mixtures) from laboratory experiments8, 12, 14, 15 and field campaigns.16 The nucleation

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rate of amine/sulfuric acid system can be three orders of magnitudes higher than that of NH3.8

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The reactions between carbonyl compounds or organic acids and amines may also contribute

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significantly to nanoparticle growth.17 Recent studies suggest that in the atmosphere carbonyl

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compounds, such as glyoxal, methylglyoxal, glycoaldehyde or hydroxyacetone form N-

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containing and oligomeric compounds with small amines in aqueous aerosols.14, 18-21 The impact

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of these aqueous reactions on secondary organic aerosol formation and brown carbon formation

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has been recently demonstrated.14, 18, 20

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In this context, the aim of this work was to improve our understanding of aldehyde-amine

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reactions in the atmosphere and to assess the potential of these reactions in the formation of

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secondary organic aerosols. In our study pinonaldehyde and dimethylamine were employed as

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model compounds for the clarification of gas phase aldehyde-amine reaction products with a

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special focus on the formation of N-containing compounds. Pinonaldehyde-DMA reactions were

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performed in Tedlar bag and reaction products were monitored with high performance analytical

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methodologies. The gaseous phase was first characterized on-line by chemical ionization mass

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spectrometry. Thecompounds from DMA-pinonaldehyde reactions were also identified by high

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performance off-line analytical techniques: by gas chromatography coupled to chemical

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ionization high-resolution quadrupole time-of-flight mass spectrometry (GC-CI-QTOF-MS) and


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Despite their high vapor

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ultra-high-performance liquid chromatography coupled to electrospray ionization Orbitrap mass

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spectrometry (UHPLC-HRMS). Formation of brown carbon was studied using liquid

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chromatography coupled with UV-Vis detector and mass spectrometry. Ambient aerosol

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samples, collected from SMEAR II boreal forest site at Hyytiälä, Finland, during August 2015,

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were analyzed by the same techniques to support the results of laboratory experiments.

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EXPERIMENTAL SECTION

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Tedlar bag experiments

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Pinonaldehyde was synthesized by oxidative bond cleavage of pinanediol (Sigma Aldrich, St.

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Louis, USA, 99 %) according to the method described by Glasius et al.22 Solid dimethylamine

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HCl (Sigma-Aldrich, St. Louis, USA, 99 %) was used to prepare DMA solution (2 mL) by

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weighing and diluting it with ultrapure water (DirectQ-UV, Millipore, USA).

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Reactivity experiments were carried out under dry conditions, at atmospheric pressure and 295 ±

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3 K in a 10 L Teflon reaction chamber (Tedlar® bag, Sigma-Aldrich), which was filled with

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nitrogen. At first, a desired volume of pinonaldehyde was injected into the bag by microliter

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syringe and evaporated slowly by applying heat from a hair dryer. Because pinonaldehyde

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decomposes easily when heated, the composition of gaseous phase has been checked after its

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evaporation to confirm the absence of degradation products. Gas phase DMA was prepared

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separately in a headspace vial (20 ml) from the solution by adding 200 µL of 5 M potassium

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hydroxide (J.T. Baker, Sweden) through the septa with a syringe. The vial was left to equilibrate

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for approximately 10 min at room temperature. A known volume of headspace was sampled

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using 5 ml gastight syringe and injected in the bag when the signalof pinonaldehyde was stable.

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Gas-phase constituents were monitored on-line using 0.1 mm i.d. deactivated fused silica


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capillary, which connected Tedlar bag with chemical ionization source of a triple quadrupole

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mass spectrometer with unit mass resolution (Bruker Scion 436-MS). Vacuum of the mass

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spectrometer was used to sample reaction mixture. Isobutane C4H10 (99.95 %, AGA), gas with

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high proton affinity (818.9 kJ/mol), was used for chemical ionization to minimize fragmentation.

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Off-line analysis

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Complementary off-line techniques were used to study the chemical composition of gas and

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condensable products. Sampling of the gas phase was performed during the reaction using

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gastight syringe (1 mL) for the analysis by gas chromatography-quadrupole-time-of-flight mass

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spectrometry (GC-QTOF-MS). Low volatile products condensed on the walls of the bag were

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analyzed by ultra-high performance liquid chromatography coupled with high resolution mass

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spectrometry (UHPLC-HRMS) after extraction with acetonitrile. Reaction products were studied

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also for their light absorbing properties (brown carbon) by adding UV-Vis spectrophotometer

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before the mass spectrometric detection.

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Gas chromatographic analysis

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A 7200 accurate-mass GC-QTOF MS instrument (Agilent Technologies, Santa Clara, USA) was

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used to identify gaseous compounds from DMA-pinonaldehyde reaction, operating in CI mode.

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The GC separation was performed using a HP-5 MS capillary column (Agilent Technologies,

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Santa Clara, USA) 30 m x 0.25 mm i.d. and a film thickness of 0.25 µm. The injector was

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operated at 250 °C and helium (purity > 99.999 %) was used as the carrier at constant pressure of

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0.76 bars. The GC oven temperature was as follows: 35 °C (held for 3 min), then 15 °C/min to

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325 °C (held for 3 min), resulting in a total run time of 25.3 min. The transfer line temperature

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was 280 °C while ion source was kept at 250 °C. TOF for MS was operated at 5 spectra/s


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acquiring the mass range m/z 70–600 with resolution of 13500. Isobutane was used as chemical

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ionization gas. Emission and electron energy were respectively fixed to 150 µA and 150 eV. The

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MS2 conditions were optimized for each compound with a quadrupole for isolation at a medium

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MS resolution and 20 was selected as collision energy. MassHunter qualitative analysis B.07 was

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used for the treatment of data.

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Liquid chromatographic analysis

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After reaction, the walls of the bag were washed with 4 × 5 mL of acetonitrile using glass

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pipette. The extracts were evaporated with a gentle stream of nitrogen until 100 µL. The final

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extracts were dissolved in 80:20 water/acetonitrile (v/v). To check for possible hydrolysis, some

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samples were dissolved in pure acetonitrile. Condensable products were analyzed with a Thermo

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Ultimate 3000 UHPLC coupled with an Orbitrap Fusion TMS (Tribrid mass spectrometer), using

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an Acquity UPLC BEH C18 column (Waters, Ireland) (50 x 2.1 mm, 1.7 µm). The eluent

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composition was (A) 0.1 % formic acid in Milli-Q grade water and (B) 0.1 % formic acid in

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acetonitrile at a flow rate of 0.6 mL/min. The mobile phase gradient was initially 95:5 (v/v, A/B),

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increased to 100 % B along 15 min and returned to 95:5 (v/v, A/B) in 1 min and then kept for 4

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min to equilibrate the column. Electrospray ionization was used in the positive mode. The

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parameters used for the mass spectrometer were the following: spray voltage 3000 V, sweep gas

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flow rate 0 respective arbitrary units (AU); sheath gas flow rate 10 AU; aux gas flow rate 5 AU;

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ion transfer tube temperature 350 °C; vaporizer temperature 300 °C; Orbitrap resolution 120 000;

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scan range m/z 50-600; maximum injection time 100 ms; automated gain control (AGC) target

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250 000; S-lens RF level, 60 %.


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Formation of the brown carbon during the reaction was studied by Agilent 1260 Infinity HPLC-

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UV-Vis system coupled with Agilent 6420 triple quadrupole mass spectrometer. The

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chromatographic conditions were the same as for the Orbitrap analysis, except for the flow rate,

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which was 0.3 mL/min and the eluent composition, which was (A) 0.01 % acetic acid in Milli-Q

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grade water and (B) 0.01 % acetic acid in acetonitrile. In addition to mass spectrum, UV-Vis

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spectrum in range from 300 to 500 nm was recorded.

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Ambient samples

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Sampling

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Boreal forest samples were collected from August 3 to August 27, 2015 at the Station for

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Measuring Forest Ecosystem-Atmosphere Relations (SMEAR II) at Hyytiälä, in southern

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Finland (61°50.845’ N, 24°17.686’ E, 179 m above sea level).23 The largest nearby city is

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Tampere, situated 60 km south west from SMEAR II station with around 200 000 inhabitants.

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Flora in Hyytiälä is dominated by Scots pine and Norway spruces.

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Samples were collected using two different set-ups (Figure S1). The size segregated samples

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were collected using a differential mobility analyzer to select a specific size of ultrafine particles

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(30 ± 6 nm particle size). Scheme of the 30 nm aerosol collection system is presented in our

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previous study24. This set-up was optimized to increase the aerosol flow rate to 9.6 L/min. The

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differential mobility analyzer was operated in a closed-loop flow arrangement with a sheath flow

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of 39 L/min. Voltages, corresponding to particle sizes of 30 nm, were preselected to collect

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particles onto PTFE filter (47 mm, 1.0 µm, Pall Corporation) placed downstream of the

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differential mobility analyzer sample flow (9.6 L/min). A timer was connected to the high

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voltage (HV) supply, which switched off the voltage and simultaneously the three-way valve to


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collect zero samples. Thus, 30 nm particles were collected for a 15 min period, and particle-free

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air was sampled onto a second filter for a further 15 min period. Before size segregation,

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particles were brought to a known charge distribution with an Am-241 alpha-source (60 MBq).

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The validation of this set-up was performed in our laboratory and in this configuration the

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aerosol size was 30 ± 6 nm (Figure S2). Total suspended particles (TSP) were collected

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simultaneously with gas phase using the set-up described in Figure S1b. TSP were collected also

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on PTFE filters at 4.7 L/min. The collection time was 72 hours for 30 nm aerosol particles and

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24 hours for TSP and gas phase sampling. As described in Figure S1b, gas phase was collected

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into two different solid phase extraction (SPE) cartridges (C8 and divinylbenzene (DVB)

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cartridges). After sampling and until analysis, filters were kept in 10 mL of acetonitrile in dark in

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a freezer at -18°C. The SPE cartridges were immediately extracted slowly with 7.5 mL of

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acetonitrile and were kept in dark in a freezer at -18°C.

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Sample preparation

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Before the analysis, test tubes with filters in acetonitrile were sonicated for 30 min. Extracts from

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filter samples and SPE cartridges were evaporated with a gentle stream of nitrogen until 250 µL

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volume was reached. Half of the sample was kept in acetonitrile for LC analysis. The other half

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of the sample was evaporated until 10 µL and reconstituted in 100 µL of dichloromethane for GC

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analysis. Ambient samples were analyzed by GC-QTOF-MS and UHPLC-Orbitrap Fusion TMS

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using the same methods as for laboratory reactivity experiments. Field blanks (particle-free air

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samples, blank filter samples and blank SPE cartridges) and laboratory blanks were extracted and

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analyzed following the same procedures to determine any potential contamination during the

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sampling, transportation, storage and the analysis.


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RESULTS AND DISCUSSION

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Table 1 presents the initial experimental conditions from pinonaldehyde-DMA reactions

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observed in this work. First experiments (R0, B0(1) and B0(2)) were performed in high

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concentrations in order to test if the formation of gaseous and condensable products from

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pinonaldehyde-DMA reactions occur and to optimize the different analytical methodologies (on-

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line analysis by CI-MS and off-line analysis by GC-CI-QTOF-MS and UHPLC-HRMS). Other

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experiments (R1, R2, R3, B1 and B2) were performed in lower concentrations. Wall losses of

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pinonaldehyde were always observed and quantified to be around 10-30 % according the

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experiments, so order of magnitude of the expected gas phase concentration was not affected.

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Since approach used here was not designed for atmospherically relevant conditions, only

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qualitative information is presented.

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On-line monitoring of the reaction mixture by CI-MS revealed decreased pinonaldehyde

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concentration after the injection of DMA (Figure S3). This observation demonstrated the

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reactivity in gas phase between DMA and pinonaldehdyde, even in “low” concentration

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(reactions R1). The formation of gaseous product was simultaneously confirmed by the increased

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m/z 196 ion signal. For the experiments R0, R2 and R3, initial increase in the abundance of the

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ion m/z 196 was followed by its decrease (Figure S3), demonstrating possible reactivity of m/z

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196 with DMA and/or pinonaldehyde. No other gaseous products in the scan range of 80 - 400

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m/z were observed, meaning that the reaction leads to the formation of low-volatile compounds,

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which are condensed on the walls of the bag. In order to get structural information of the gaseous


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and condensable products, high resolution off-line GC-QTOF-MS and UHPLC-HRMS analysis

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(MS2 or MS3) were performed and the results are described below.

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Gaseous products from pinonaldehyde-DMA reaction

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GC-QTOF-MS base peak chromatograms (BPCs) of m/z 169.1223 (pinonaldehyde, C10H17O2+)

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and the product of the reaction between pinonaldehyde and DMA m/z 196.1696 (± 3 ppm)

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together with its fragmentation pattern are shown in Figures 1a and 1b. Difference between

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theoretical and measured masses obtained by TOF-MS are small and well within commonly

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acceptable errors (i. e, ± 5 ppm). These results demonstrate the formation of m/z 196.1696

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products in gas phase during all the experiments. Gaseous products (m/z 196.1696) were not

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observed in the blank experiments (B0(1), B0(2), B1 and B2). The analysis revealedthat there are

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three isomers formed in the reaction. Based on the accurate mass measurements combined with

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fragmentation patterns(Figure 1b), evidence of nitrogen containing compounds was confirmed in

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our experiments. Accurate masses of these three compounds indicate that their [M + H]+ ion

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formula is C12H22NO+. The CI and EI spectra of these three isomers are given in Figure S4. MS2

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experiments show that all isomers produce the same fragments, but their ratios slightly differ.

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The main gaseous compound (Figure 1a, iii) accounts for 94 ± 3 % of the gaseous reaction

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products detected from pinonaldehyde-DMA experiments.

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The m/z 196.1696 ions were also observed by UHPLC-HRMS from the acetonitrile extract of the

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walls of the bag after DMA-pinonaldehyde experiments. Figures 2a and 2b present respectively

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the MS2 fragmentation pattern of the main m/z 196.1696 ion and the MS3 fragmentation pattern

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of the fragment ion m/z 126.1278. The neutral loss of C2H7N (45.0578) is consistent with the

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formation of amine reaction product, especially from dimethylamine. The MS2 fragmentation


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pattern from GC-QTOF-MS analysis shows the formation of acetaldehyde ion m/z 43.0178

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(C2H3O+), demonstrating that the reaction between DMA and pinonaldehyde occurred on the

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aldehyde function. Figure 1b, 2a and 2b show the formation of m/z 71.0491 (C4H7O+) product

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ion and m/z 126.1277 (C8H16N+) product ion (rupture of the cyclobutane moieties), confirming

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the structure of the main gaseous product from pinonaldehyde-DMA reaction presented in the

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Figure 2c. The proposed MS2 fragmentation pathway of the ion m/z 196.1696 is given in Figure

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S5.

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The chemical formulas of these isomers, based on high resolution MS, were confirmed to be

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C12H21ON, thus corresponding to chemical structure with degree of unsaturation of 3 (Figure 2c).

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The MS2 fragmentation patterns of the isomers are similar, proving the formation of

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configurational isomers (geometric or optical isomers). The structure proposed in Figure 2c is in

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the agreement with the mechanism proposed by Qiu and Zhang,17 suggesting the formation of

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enamine compound from the reaction between the carbonyl and secondary amine functionalities.

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Accordingly it is obvious that DMA reacts on the aldehyde function to give carbinolamines

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which then dehydrate to give enamine compounds.25 The structure of these compounds are

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similar to some N-containing compounds which play an important role in the chemistry of

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atmospheric brown carbon,26 suggesting that DMA-pinonaldehyde may be important not only for

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secondary organic aerosol formation but also for the formation of brown carbon. As presented in

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a recent review on multiphase chemistry of atmospheric amines,17 the carbonyl group can react

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with secondary amines to form enamine compounds. These compounds may condense on or be

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partitioned into the particle-phase and engage in heterogeneous reactions. The formation of

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imines, enamines and polymerized products from the reaction between amines and carbonyl


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compounds in bulk solution or particle phase reactions have been also demonstrated

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previously.27

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In order to assess atmospheric relevance of them/z 196.1696, its vapor pressure was determined

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using gas chromatographic approach developed in our laboratory. Briefly, the method is based

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on relation between vapor pressure and the retention time in GC. Compounds with similar

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functionality and known vapor pressure values eluting before and after the studied compound are

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used as references for the calculation.28 Vapor pressure was found to be (7.7 ± 0.5) × 10-3 Torr at

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298 K, being 10 times lower than the vapor pressure of pinonaldehyde and in the same order of

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magnitude as that of pinonic acid.29 Thus, it is clear that the product has high potential to

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participate in the formation of secondary organic aerosol in the atmosphere. Moreover, relatively

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low vapor pressure explains why the compound was seen in both gas and liquid phases.

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Formation of low-volatile compounds from pinonaldehyde-DMA reaction

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Figure 3 presents total ion chromatograms (TICs) from the DMA-pinonaldehyde reaction sample

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(3a) and from the pinonaldehyde sample (3b) obtained by Orbitrap UHPLC-HRMS analysis.

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Based on the accurate mass measurements (Table 2), evidence of N-containing low-volatile

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compounds was confirmed under our experimental conditions from the extraction samples of the

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bag walls. Differences between the theoretical and measured masses are very small and well

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within commonly acceptable errors (i. e. < ± 3 ppm). According to our knowledge, this is the

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first time when these compounds are reported in the literature. Our results are in agreement with

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previous studies that have demonstrated the formation of N-containing oligomeric compounds

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from small carbonyl compound and amines.14, 18


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As discussed in the previous section, m/z 196.1696 ions were also detected in condensable phase,

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demonstrating that these compounds may be partitioning between gas and particle phase in

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ambient conditions. Another C12 compound was detected in our experimental conditions with

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accurate mass suggesting formula of C12H24ON+ for the protonated molecular ion. High-

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molecular weight nitrogen containing compounds (MW > 360 Da), such as those containing one

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DMA and two pinonaldehydes (dimeric structure), were also detected. At least two isomers of

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m/z 364.2846 (C22H38O3N+) and five isomers of m/z 380.2795 (C22H38O4N+) were observed in

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the analysis of condensation products (Table 2). The accurate mass measurements of their

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corresponding [M + H]+ ions indicate the formation of C22 carbon compounds. Liggio et al.,30

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proposed the formation of pinonaldehyde dimers which can react further with DMA and explain

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the formation of these low volatile N-containing compounds. The formation of m/z 196.1696,

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m/z 198.1853, m/z 364.2846 and m/z 380.2795 were observed in all the experiments (excluding

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blanks). In high concentration conditions (reaction R0), ions with m/z 532.3996 were also

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detected. The accurate masses of these [M + H]+ ions indicate that their formula is C32H54O5N+.

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However, most probably these compounds are not formed in ambient conditions because they

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were not observed during the low concentration experiments R1, R2 and R3. The same results

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for the condensation products were obtained also with the APCI, which further proves that these

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products were formed in the reaction and not in the MS ionization process (adduct and cluster

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formation should be different compared to ESI). These results suggest the potential role of

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DMA-pinonaldehyde reaction and more generally aldehyde-amine reactions to participate in the

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formation of N-containing low-volatile organic compounds. Analogs of these products were also

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observed previously during the reaction between ozonolysis oxidation products from limonene or

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α-pinene and ammonia.31-33 Previous field measurements have also demonstrated the occurrence


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of N-containing high-MW compounds with carbon-nitrogen bonds in urban aerosols, suggesting

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that carbonyl-amine reactions may be an important source of nitrogen-containing compounds in

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the aerosol-phase in the atmosphere.34 Because pinonaldehyde is present in particle phase in the

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atmosphere,35 multiphase chemistry of atmospheric amines with pinonaldehyde may take place.

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Futhermore, water in particles can catalyze the heterogeneous aldehyde-amine reactions.17 Water

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is also important for dimerization via hydrates36 which could explain the higher mass products

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obtained here.

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Interestingly, the extracts from experiments R0 were yellow, suggesting that DMA-

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pinonaldehyde may play a role in brown carbon formation. Thus, we evaluated the ability of

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DMA-pinonaldehyde to form light-absorbing species, as demonstrated in aqueous phase

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reactions of small carbonyl compounds and amines.20, 37 Previous studies have also demonstrated

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the formation of brown carbon from carbonyl compounds from ozonolysis of α-pinene and

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limonene with NH3.31-33, 38 These studies have highlighted the significant fraction of carbonyl-

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imine conversion products. As can be seen in Figure S6, condensable products indeed absorb

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radiation in the range from 300 to 500 nm. The Figure shows separately absorption spectra for

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m/z 196 and two dimers (m/z 364, 380) as well as the average absorption spectra for the whole

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chromatogram. Note, that in contrast to m/z 196, dimers have high absorption demonstrating that

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they might play an important role for brown carbon formation. UV-Vis chromatogram differs

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significantly from the MS chromatogram, namely the former suggests that the studied reaction

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produces much more brown carbon compounds, compared to the results obtained by MS.

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Interestingly, the reaction between pinonaldehyde and ammonia did not result in formation of

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brown carbon species in liquid phase as was shown by Nguyen et al.39 Our results indicate that


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the chemistry of dimethylamine is different.31-33,

38

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clear, but its study in detail requires additional experiments and was out of scope of this research.

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Atmospheric evidence of N-containing compounds from DMA-pinonaldehyde reaction in

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Boreal forest samples

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Figure 4 shows the comparison of base peak chromatograms (BCPs) for the ion m/z 196.1696

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and m/z 380.2795 for (A) DMA-pinonaldehyde reactions, (B) 30 nm sample (August 14-17,

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2015), (C) TSP sample (August 14-15, 2015), and for (D) DVB cartridge SPE (August 14-15,

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2015). Based on good agreement between the retention times and the accurate masses obtained,

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the m/z 196 and m/z 380 found in the boreal forest samples were attributed to the N-containing

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compounds from pinonaldehyde-DMA reactions. The other reaction products identified in

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laboratory experiments were not observed in the boreal forest samples.

318

At least four isomers of m/z 196 were detected from the laboratory experiments but only one

319

from ambient samples (RT 4.97 min). Detection of the ion with m/z 196 also in ambient gas

320

phase samples agrees with the results from the laboratory experiments. Two compounds

321

(C12H21ON and C22H37O4N) were detected in TSP and 30 nm aerosol samples, meaning that

322

DMA-pinonaldehyde reactions may play an important role in the first step of the formation of

323

new particles in the atmosphere. Quantification was not possible in this work, since sufficient

324

amount of synthesized and purified compounds was not available. Nevertheless, it would be

325

worthwhile to quantify these compounds in future studies to estimate their contribution to the

326

formation of SOA in the atmosphere. Figure 5 presents the peak area divided by the sampling

327

volume (in liters) of m/z 196.1696 (RT 4.97 min) and m/z 380.2795 ions (RT 6.30 min) for the

High brown carbon formation potential is


15


Page 16 of 26

328

30 nm aerosol samples as well as the 28.2 + 31.6 nm aerosol concentration from differential

329

mobility particle sizer in Hyytiälä.40

330

As shown in Figure 5, the trend of m/z 196.1696 ion is in good agreement with the number

331

concentration of 30 nm aerosols in the atmosphere, except for sample 2 (August 6-10, 2015) and

332

sample 3 (August 10-14, 2015). No correlation was found with meteorological parameters, with

333

the concentration of atmospheric oxidants or with the concentration of monoterpenes to explain

334

the low concentration of m/z 196.1696 ions in sample 2 and 3. The m/z 380.2795 ion was

335

observed only in one sample (14-17 of August 2015) with the highest concentration of 30 nm

336

aerosol particles. As presented in supplementary information (Figure S7), the three days

337

measured (14-17 August 2015) were characterized by high nucleation events, suggesting a direct

338

link between the formation of these compounds and the formation of new particles in the

339

atmosphere. Figure S8 presents the identification of these compounds in TSP samples during

340

August, 2015. From the total of 23 samples, C12H21ON and C22H37O4N compounds were

341

detected in ten and four samples during this field campaign in the boreal forest. Our results prove

342

that the two compounds, C22H21ON and C22H37O4N, can be formed also under ambient

343

conditions.

344

In this study, new evidence was achieved on the nitrogen-containing compounds originating

345

from DMA-pinonaldehyde reaction in both laboratory experiments and ambient air (gas and

346

aerosol phase) sampled in the boreal forest at Hyytiälä, Finland. Because aldehyde compounds

347

and amines are ubiquitous in the atmosphere, the reactions in gas phase or the heterogeneous

348

reactions between these compounds could be important for the formation and growth of SOAs in

349

the atmosphere. These observations suggests the potential impact of amine-aldehyde chemistry

350

in remote forested atmosphere. Furthermore, the reactions could be likely acid-catalyzed, since


16

Page 17 of 26


351

sulfuric acid, nitric acids or organic acids are commonly available in the atmospheric particle-

352

phase. However, more studies are needed to quantify these compounds in ambient samples and

353

to elucidate their formation pathways. The experimental approach described in this study was

354

efficient for the preliminary screening of possible reactions and their products on-line with the

355

possibility of collecting samples for the off-line GC and UHPLC analysis with HRMS detection.

356

Additional confirmation of the results from the reaction experiments could be done in smog

357

chamber with more atmospherically relevant conditions.

358 359 360

FIGURES

(iii)

1(a)

(i)

126.1281

1(b) 71.0499 43.0179

(ii)

+

C4H7O + C2H3O (+2.81 ppm) (+2.32 ppm)

(iii)

+

C8H16N (+1.58 ppm) 111.1045 +

C7H13N (+1.80 ppm)

196.1700 +

C12H22ON (+2.04 ppm)

361 362

Figure 1: 1(a) GC-QTOF-MS base peak chromatograms (BPCs) of m/z 169.1223

363

(pinonaldehyde – green) and m/z 196.1696 (reaction products – red) ions observed in Tedlar bag


17


Page 18 of 26

364

experiments injected by gas tight syringe (1.0 mL) from DMA-pinonaldehyde reaction by GC-

365

QTOF-MS, 1(b) MS2 fragmentation pattern of m/z 196.1696 ion (iii). Chemical ionization with

366

isobutane.

367 368 369 370


18

Page 19 of 26


+

C8H16N (+ 0.82 ppm)

Relative Abundance

2(a) +

C12H22ON (- 0.01ppm)

C4H6O (- 1.49 ppm) +

C8H11 (+1.61 ppm)

C10H15O (- 0.18

C2H4O (- 2.42 ppm)

+

C2H7N (- 0.64 ppm)

Relative Abundance

m/z

m

2(b)

+

C8H16N (+ 1.38 ppm)

C2H7N (- 1.97 ppm) +

+

C6H9

C7H13N

(+2.06 ppm)

(+3.24 ppm)

m/z

2(c) CH3 O

N CH3

H3C

371

H3C

CH3

372

Figure 2: 2(a) MS2 of m/z 196.1696 ion and 2(b) MS3 of m/z 126.1277 ion by Orbitrap UHPLC-

373

HRMS with electrospray ionization (ESI), and 2(c) proposed structure of the main reaction

374

product

375

dimethylcyclobutyl}ethanone.

from

pinonaldehyde-DMA

reaction,

1-{3-[2-(dimethylamino)vinyl]-2,2-

376 377


19


Page 20 of 26

m/z 380 m/z 198, coeluted

Relative Abundance

Relative Abundance

RT: 1.17 – 7.81 RT: 1.17 - 7.81 100 80

m/z 196 4.79 2.65

4.73

60 40

4.98 4.98

m/z 169 pinonaldehyde 4.28 3.78

3(a)

7.37 NL: 2.78E9 m/z 364 6.64 7.29 7.66 TIC MS M15110905 6.96

4.35

6.30

20

NL: 1.06E9 TIC MS M15110906

2.70 2.70

100 80 60

3(b) 7.66

40 20 2

3

4

5

6

7

378

Time (min)

379

Figure 3: Total ion chromatograms (TICs) from DMA-pinonaldehyde reactions (3a) and from

380

pinonaldehyde (3b) by Orbitrap UHPLC-HRMS using electrospray ionization (ESI).

381

382 383

Figure 4: Base peak chromatograms of m/z 196.1696 ± 0.0003 and m/z 380.2795 ± 0.0003 by

384

UHPLC-HRMS from (A) pinonaldehyde-DMA laboratory experiments, (B) 30 nm aerosol

385

sample (August 14-17, 2015), (C) TSP sample (August 14-15, 2015), and (D) gas phase

386

collected by DVB SPE cartridge (August 14-15, 2015).


20


Area of peak/Sampling volume

6

m/z 196.1696 (RT 4.97 min) m/z 380.2795 (RT 6.30 min) 28.2 + 31.6 nm aerosol

7000 6000

5

5000

4

4000 3 3000 2

2000

1

1000

0

0

#particles/cm3

Page 21 of 26

387

Figure 5: Relative abundance normalized to sample volume (L) of protonated molecular ions m/z

388

196.1696 and m/z 380.2795 in 30 nm aerosol samples and the number concentration of 30 nm

389

aerosol particles at Hyytiälä, Finland from 3rd to 27th of August 2015

390

TABLES

391

Table 1: Summary of the experimental conditions of Tedlar bag experiments and identification

392

of gaseous product by GC-QTOF-MS analysis using chemical ionization. The presence of

393

gaseous products is indicated by + and absence by -. Experiment

Pinonaldehyde (ppm)

DMA (ppm)

Gaseous product

Number of repetitions

R0

100

1000

+

3

R1

1.0

1.0

+

3

R2

1.0

10.0

+

3

R3

3.0

30.0

+

3

B0(1)

100

0

-

1

B0(2)

0

1000

-

1

B1

0

1.0

-

3

B2

1.0

0

-

3

394


21


Page 22 of 26

395

Table 2: Protonated N-containing compounds found by UHPLC-HRMS analysis in the

396

condensable phase of the DMA-pinonaldehyde reaction. [M+H]+ detected ions (m/z)

Molecular formula

∆m (ppm)

Experiments

196.16959

C12H22ON

+

- 0.01

R0, R1, R2, R3

198.18531

C12H24ON+

- 0.35

R0, R1, R2, R3

364.28461

C22H38O3N+

- 0.04

R0, R1, R2, R3

380.27939

C22H38O4N+

- 0.38

R0, R1, R2, R3

532.39984

+

- 0.36

R0

C32H54O5N

397 398

ASSOCIATED CONTENT

399

Supporting Information.

400

Figure S1 presents the scheme of the 30 nm aerosol collection system and the scheme for the

401

collection of TSP and gas samples used at Hyytiälä in August 2015. Figure S2 presents the

402

validation of the set-up of 30 nm aerosol collection. Figure S3 presents the on-line monitoring

403

plot of the reaction between DMA and pinonaldehyde by CI-MS. Figure S4 shows the CI and EI

404

spectra from the three gaseous reaction products detected by GC-QTOF-MS. Figure S5 presents

405

the MS2 fragmentation pathway of the ion m/z 196. Figure S6 presents the chromatograms of

406

condensable products with UV-Vis and MS detectors. Figure S7 presents the new particles

407

formation events observed in Hyytiälä from August 14th to 18th, 2015. Figure S8 presents the

408

variation of UHPLC peak areas of ions m/z 196.1696 and m/z 380.2795 detected by HRMS in the

409

TSP samples from Hyytiälä from the 4th to 26th of August 2015. This material is available free of

410

charge via the Internet at http://pubs.acs.org.

411

AUTHOR INFORMATION

412

Corresponding Author

413

*Marja-Liisa Riekkola. Tel: +358 405058848. E-mail address: [email protected]

414


22

Page 23 of 26


415

Notes

416

The authors declare no competing financial interest.

417

ACKNOWLEDGMENT

418

The financial support of the Academy of Finland Center of Excellence program (project no

419

272041) is gratefully acknowledged. Martin Söderström is thanked for the help with LC-HRMS

420

analysis and Charlotte Jones for the help in the laboratory. Agilent Technologies is

421

acknowledged for the technical support and cooperation. Technical staff at the SMEAR II

422

Station are thanked for the valuable help.

423 424

REFERENCE

425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450

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- H2O

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Nitrogen-Containing Low Volatile Compounds from Pinonaldehyde

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